A high pressure rotary nozzle device having a rotating shaft is disclosed in my U.S. Pat. No. 7,635,096, which is incorporated herein by reference in its entirety. The hollow shaft in this device rotates within a fixed housing wherein the axial force which acts upon the shaft due to the fluid pressure at the shaft inlet is balanced, eliminating the need for mechanical bearings.
This nozzle is particularly well suited to industrial uses where the operating parameters can be in the range of 1,000 to 40,000 psi, rotating speeds of 1000 rpm or more and flow rates of 2 to 50 gpm. The hollow shaft in this device is provided with a “bleed hole” leading from the central bore through the hollow shaft to its exterior. This allows a small portion of pressurized fluid to reach a chamber formed within the nozzle housing outside the exterior of the forward portion of the nozzle shaft. The fluid pressure in this chamber acts upon the nozzle shaft with a sufficient axial component so as to balance the corresponding axial component against the nozzle shaft created by the internal fluid pressure. This chamber, or passage has a frusto-conical tubular shape surrounding a corresponding tapered portion of the shaft which further allows the fluid to flow between the nozzle housing and the shaft to facilitate and lubricate the shaft as it rotates.
Because of the frusto-conical tapered shape of both the exterior surface of the shaft and the complementary interior surface of the housing, the spacing between the housing and the shaft varies slightly with axial movement of the shaft. This movement creates a self balancing effect in which the axial forces upon the shaft remain balanced and there is always some fluid flowing between the shaft and housing which helps decrease contact and resulting wear between these two components.
The rotation of such a nozzle is provided by the reaction forces experienced by the nozzle tip as a result of the redirection of fluid flow outward through offset angled ports in the nozzle tip offset from the longitudinal axis of the nozzle. The redirection of flow is offset from the axis of the nozzle shaft such that the reaction forces apply a torque to the nozzle shaft and tip. At such high pressures the offset angled ports are more than sufficient to provide rotation, or swivel, of the nozzle about its longitudinal axis. A small detachable jet head having a diameter smaller than the body of the nozzle can be attached at the leading end of the nozzle to provide an improved coverage pattern for the high-pressure fluid.
Unless the nozzle tip, i.e., the jet head, has offset angled ports, rotation of the nozzle shaft is not likely to occur. There are some applications, however, where offset angled ports are either undesirable due to a change in driving torque when pressure or flow rate is changed, and undesirable because driving rotation by this method produces very high rotation speeds (20,000-30,000 rpm), Thus there is also a need for a rotary nozzle that is axially self balanced as above described, but in which the rotary nozzle shaft is driven by a method resulting in slower rotation speeds, in a range on the order of 2000 to 4000 rpm, rather than relying on offset angled reaction forces to provide the rotational force on the nozzle shaft.